Mixtures of 3,5- and 2,4-dihalo-1-alkylbenzenes and especially mixtures containing 3,5-dichlorocumene and 2,4-dichlorocumene are readily prepared by reacting a m-dihalobenzene with an alkylating agent in the presence of an aluminum chloride Friedel-Crafts catalyst as taught in Dreisbach et al., U.S. Pat. No. 2,186,960. However, such mixtures, especially isomeric mixtures, are difficult to separate by conventional separatory procedures because of like physical properties. For example, separation of many isomeric mixtures by distillation is extremely difficult, if not impossible, because the boiling points of many of the individual components are almost identical.
In view of the severe difficulties existent in the conventional processes for preparing and separating such compounds from isomeric mixtures thereof, it would be highly desirable to provide an improved process for separating such isomers.
Such separation procedures can be found in Dewald and Markley, U.S. Pat. No. 4,059,642 and U.S. Pat. No. 4,104,315, which teach processes which comprise contacting an isomeric mixture of ar-dihalo-ar-alkylbenzenes with an alkylating agent in the presence of a Friedel-Crafts catalyst at a reaction temperature less than about 90.degree. C. such that the isomer having substituents in the 1,2,4-ring positions is preferentially alkylated. The alkylated isomer is then readily separated from the remaining unreacted isomer by simple distillation. While these procedures are effective, other procedures are still being sought.